add go 1.13 for travis ci

Hideo Hattori · Hideo Hattori · commit 5eef3a63b323 · 2020-02-06T18:57:15.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -4,6 +4,7 @@ sudo: false
 matrix:
     include:
         - go: 1.9
+        - go: "1.13"
         - go: tip
 
 install:
